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Updated: Jun 27, 2025

Characterizing Lewis Pairs Using Titration Coupled with In Situ Infrared Spectroscopy
Published on: February 20, 2020
Appended Lewis Acids Enable Dioxygen Reactivity and Catalytic Oxidations with Ni(II)
Daniel M Beagan1, Carolina Rivera1, Nathaniel K Szymczak1
1University of Michigan, 930 N. University Ave., Ann Arbor, Michigan 48109, United States.
Abstract:
We disclose a suite of Ni(II) complexes featuring secondary sphere Lewis acids of varied Lewis acidity and tether lengths. Several of these complexes feature atypical behavior of Ni(II): reactivity with O2 that occurs only in the presence of a tethered Lewis acid. In situ UV-vis spectroscopy revealed that, although adducts are stable at -40 °C, complexes containing 9-borabicyclo[3.3.1]nonane (9-BBN) Lewis acids underwent irreversible oxidative deborylation when warmed to room temperature. We computationally and experimentally identified that oxidative instability of appended 9-BBN moieties can be mitigated using weaker Lewis acids such as pinacolborane (BPin). These insights enabled the realization of catalytic reactions: hydrogen atom abstraction from phenols and room temperature oxygen atom transfer to PPh3.
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